Device and method for detecting malfunctions in a fuel injection system provided with a fuel pressure damper

Abstract

In the low pressure zone ( 10 ) of a fuel injection system a fuel pressure damper ( 12 ) is provided which dampens pressure variations, especially such pressure variations that are caused by operation of a high-pressure fuel pump ( 16 ) mounted downstream of the low pressure zone ( 10 ). In the low pressure zone ( 10 ), the pressure profile is detected by a pressure sensor ( 14 ). The high-frequency components of the pressure profile detected by the pressure sensor ( 14 ) can be used to ascertain whether the fuel pressure damper ( 12 ) functions properly.

1. A device for the detection of faults in a fuel injection system, comprising:
 a low-pressure zone; 
 a fuel pressure damper located in the low-pressure zone; and 
 at least one pressure sensor for sensing the pressure which prevails in the low-pressure zone, wherein 
 a malfunction of the fuel pressure damper is recognized by reference to a high-frequency component of a first signal, supplied by the pressure sensor, which characterizes the pressure/time trace in the low-pressure zone. 
 
   
   
     2. The device in accordance with  claim 1 , wherein
 the first signal is low-pass filtered to enable a low-pass filtered second signal to be generated; 
 a third signal is generated as an absolute difference between the first signal and the second signal; and 
 the third signal is compared with a prescribed threshold value, whereby if the threshold value is exceeded it is concluded that there is a malfunction of the fuel pressure damper. 
 
   
   
     3. The device in accordance with  claim 1 , wherein
 the first signal is subjected to a Fourier transformation to generate a frequency spectrum which corresponds to a time-trace of the first signal, and 
 the high-frequency component of the frequency spectrum is compared with at least one prescribed threshold value, whereby if the threshold value is exceeded it is concluded that there is a malfunction of the fuel pressure damper. 
 
   
   
     4. The device in accordance with  claim 1 , wherein the fuel injection system has a high-pressure fuel pump and a high-pressure zone with a fuel store. 
   
   
     5. The device in accordance with  claim 1 , wherein a malfunction of the fuel pressure damper is recognized can be stored in a fault memory. 
   
   
     6. The device in accordance with  claim 1 , wherein the recognition of a malfunction of the fuel pressure damper is effected taking into account operating conditions in an internal combustion engine. 
   
   
     7. The device in accordance with  claim 1 , wherein the fuel injection system is provided with at least one control unit, in which at least one of the above-mentioned analyses is performed. 
   
   
     8. The device in accordance with  claim 1 , wherein the device has an interface for installation in a vehicle. 
   
   
     9. The device in accordance with  claim 1 , wherein the device has an interface for installation in a diagnostic facility which is separate from the vehicle. 
   
   
     10. A method for recognizing faults in a fuel injection system in which the fuel injection system has a low-pressure zone, a fuel pressure damper located in the low-pressure zone, and at least one pressure sensor for sensing the pressure which prevails in the low-pressure zone, comprising:
 sensing a pressure/time trace in the low-pressure zone; 
 generating a first signal which characterizes the pressure trace in the low-pressure zone; and 
 analyzing a high-frequency component of the first signal in order to recognize from it a malfunction, of the fuel pressure damper. 
 
   
   
     11. The method in accordance with  claim 10 , wherein
 the first signal is low-pass filtered, so that a low-pass filtered second signal is generated, 
 a third signal is generated as an absolute difference between the first signal and the second signal, and 
 the third signal is compared with a prescribed threshold value, whereby if the threshold value is exceeded it is concluded that there is a malfunction of the fuel pressure damper. 
 
   
   
     12. The method in accordance with  claim 10 , wherein
 the first signal is subjected to a Fourier transformation, to generate a frequency spectrum corresponding to the time-trace of the first signal, and 
 the high-frequency component of the frequency spectrum is compared with at least one prescribed threshold value, whereby if the threshold value is exceeded it is concluded that there is a malfunction of the fuel pressure damper. 
 
   
   
     13. The method in accordance with  claim 10 , wherein the fuel injection system has a high-pressure fuel pump and a high-pressure zone with a fuel store. 
   
   
     14. The method in accordance with  claim 10 , wherein a malfunction which is recognized in the fuel pressure damper is stored in a fault memory. 
   
   
     15. The method in accordance with  claim 10 , wherein the recognition of a fuel pressure damper malfunction is effected taking into account the operating conditions of the internal combustion engine. 
   
   
     16. The method in accordance with  claim 10 , wherein the fuel injection system has at least electronic one control unit assigned to it, in which at least one of the above-mentioned analyses is performed. 
   
   
     17. The method in accordance with  claim 10 , wherein emergency measures are initiated if a malfunction of the fuel pressure damper is detected. 
   
   
     18. A vehicle with a device for recognizing faults in a fuel injection system, the device comprising:
 a low-pressure zone; 
 a fuel pressure damper located in the low-pressure zone; and 
 at least one pressure sensor for sensing the pressure which prevails in the low-pressure zone, wherein 
 a malfunction of the fuel pressure damper is recognized by reference to a high-frequency component of a first signal, supplied by the pressure sensor, which characterizes the pressure/time trace in the low-pressure zone. 
 
   
   
     19. A diagnostic facility with a device, for recognizing faults in a fuel injection system on a vehicle, which is located off the vehicle, the device comprising:
 a low-pressure zone; 
 a fuel pressure damper located in the low-pressure zone; and 
 at least one pressure sensor for sensing the pressure which prevails in the low-pressure zone, wherein 
 a malfunction of the fuel pressure damper is recognized by reference to a high-frequency component of a first signal, supplied by the pressure sensor, which characterizes the pressure/time trace in the low-pressure zone.